JP3379655B2 - Magneto-optical disk reproduction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk reproducing system, and more particularly to a magneto-optical disk reproducing system for reproducing an edge-recorded magneto-optical disk medium.

The magneto-optical disk is originally a high-density memory, but in recent years, with the rapid development of multimedia,
There has been a demand for further miniaturization and high density as a core memory. For this reason, the edge recording method has been put into practical use as one means of increasing the recording density, but it is expected that the recording density will be improved by further reducing the recording marks.

[0003]

2. Description of the Related Art The edge recording method is shown in FIG. 5 (A) in which (2,7) RLL code (run length limited code) recording data is inverted at a position of "1". The laser diode is caused to emit light in the light emission pattern of the waveform shown in (B), thereby heating the magneto-optical disk medium having the perpendicular magnetization film to which an external magnetic field is applied to heat the magneto-optical disk medium, and the magnetization reversal region (magnetic domain) shown by diagonal lines in FIG. ) Is formed. The edge of this recording mark corresponds to "1" of the recording data.

When reproducing this, the reproducing laser beam spot is irradiated to the above magnetic distinction to utilize the magnetic Kerr effect,
A reproduction waveform shown in FIG. 7D corresponding to the direction of magnetization is obtained, the reproduction waveform is sliced into a rectangular wave, the edge position is detected from the inversion position thereof, and if there is an edge based on the synchronous clock, a true value " If there is no edge, and the edge has no false value, the recorded data is reproduced.

However, since the magneto-optical disk carries out thermomagnetic recording, the length of the recording mark becomes longer or shorter depending on the sensitivity of the magneto-optical disk medium, the environmental temperature at the time of recording, and the variation of the power of the recording laser beam. It changes and changes.
The amount of change in the length of the recording mark does not depend on the length of the mark itself, and the length of the recording mark changes uniformly for long recording marks and short recording marks.

An apparatus for synchronizing the phases of the rising and falling edges of a recording mark by utilizing this is described in Japanese Patent Laid-Open No. 3-32132.

This conventional device has the configuration shown in FIG. 6, and the reproduction waveform a coming into the terminal 10 as shown in FIG.
The binarizing unit 11 compares the slice level with the slice level to obtain the binarized signal b shown in FIG. Next, the front and rear edge separation unit 12
The rising edge and the falling edge of the binarized signal b are separated to obtain edge signals c and d shown in FIGS. 7C and 7D, respectively.

The edge signal c is supplied to a PLL (Phase Locked Loop) 13 and a data discriminator 14, and the PLL
The synchronization clock e shown in FIG. 7E generated in synchronization with the edge signal c at 13 is supplied to the data discriminating unit 14.
The data discriminating unit 14 synchronizes the edge signal c with the synchronizing clock e to generate the signal g shown in FIG. Similarly, the edge signal d is supplied to the PLL 15 and the data discriminating unit 16, and the edge signal d is supplied by the PLL 15.
The synchronization clock f shown in FIG. 7 (F) generated in synchronization with
Are supplied to the data discrimination unit 16. The data discriminating unit 16 synchronizes the edge signal d with the synchronization clock f to generate a signal h shown in FIG. 7H in which noise jitter is removed.

The above signals g and h are sent to the synthesizing section 17 as shown in FIG.
After the combined signal i shown in (I) is obtained, the data discriminating unit 18
7 is synchronized with the synchronization clock e to produce the reproduction data shown in FIG. 7 (J), which is output from the terminal 19. The synchronous clock e is output from the terminal 20 together with the reproduced data.

[0010]

If the length of the recording mark is shortened for high density recording, the clock period also becomes shorter and the phase shift becomes relatively large.

However, the signal g shown in FIG.
8C is synchronized with the synchronous clock e shown in FIG. 8C, and the signal h shown in FIG.
The synthesized signal j shown in (D) is generated. At this time, assuming that the period of the synchronous clock e is T, the signal h in the range of ± T / 2 from the rising edge of the synchronous clock e is phase-shifted to the rising edge position of the synchronous clock e. That is, the signal h is only allowed from the rising edge of the synchronous clock e (that is, the rising edge of the signal g) to a phase shift of ± T / 2 or less, and there is a problem that the allowable range is narrow.

The present invention has been made in view of the above points,
It is possible to provide a magneto-optical disk reproducing method capable of expanding the allowable range of the phase shift between the rising edge signal and the falling edge signal and enabling high-precision reproduction even when recording marks are made small and high-density recording is performed. To aim.

[0013]

The magneto-optical disk reproducing method of the present invention is applied to a magneto-optical disk medium having a perpendicular magnetization film,
A rising edge signal and a falling edge signal indicating the leading edge and the trailing edge of the recording mark are formed from the reproduction waveform obtained by irradiating the recording mark with a reproduction light spot by forming a recording mark with the edge position corresponding to the recording data. And the first and second edges obtained from the rising edge signal and the falling edge signal, respectively.
After performing the data discrimination of each of the rising edge signal and the falling edge signal by using the synchronous clock of No. 3, the both data discrimination signals are combined, and further the data discrimination is performed by using the third synchronous clock to obtain reproduced data. It is a magneto-optical disk reproducing system, and has a clock generation unit for generating a third synchronous clock synchronized with the central position of the phase difference between the first synchronous clock and the second synchronous clock.

[0014]

In the present invention, since the third synchronous clock is synchronized with the center position of the phase difference between the first synchronous clock and the second synchronous clock, the rising edge signal and the falling edge signal are ± 1 / for 3 sync clocks
A phase shift of up to 2 sync clock cycles is allowed,
The phase shift between the rising edge signal and the falling edge signal is allowed up to ± 1 synchronization clock cycle.

[0015]

1 is a block diagram of an embodiment of the method of the present invention. In the figure, the same parts as those in FIG. 6 are designated by the same reference numerals.

In FIG. 1, FIG.
The reproduced waveform a as shown in (A) is compared with the slice level in the binarization unit 11 to obtain the binarized signal b shown in FIG. 2 (B). Next, the front and rear edge separation unit 12 separates the rising edge and the falling edge of the binarized signal b to separate them from each other as shown in FIG.
(D) Obtain the respective edge signals c and d shown in FIG.

The edge signal c is supplied to a PLL (Phase Locked Loop) 13 and a data discriminator 14, and the PLL
The first synchronization clock e shown in FIG. 2E generated in synchronization with the edge signal c at 13 is supplied to the data discriminating unit 14. The data discriminating unit 14 synchronizes the edge signal c with the synchronization clock e to generate a signal g shown in FIG. Similarly, the edge signal d is PLL15.
2F is supplied to the data discriminating unit 16 and is generated in the PLL 15 in synchronization with the edge signal d, and the second synchronizing clock f shown in FIG. The data discriminating unit 16 synchronizes the edge signal d with the synchronization clock f to generate a signal h shown in FIG. 2 (H) from which noise jitter is removed.

The above signals g and h are combined by the synthesizing section 17 as shown in FIG.
After the combined signal i shown in (I) is obtained, the data discriminating unit 18
Is supplied to.

The synchronous clocks e and f output from the PLLs 13 and 15 are supplied to the clock generator 30.
The PLLs 13 and 15 perform a phase comparison between the edge signal and the self-output synchronous clock, and the phase difference voltage produces a VC.
While the oscillation frequency of O (voltage controlled oscillator) is controlled, the clock generation unit 30 has the configuration shown in FIG.

In FIG. 3, the synchronous clocks e and f coming from the terminals 31 and 32 are phase comparators 33 and 34, respectively.
Third synchronous clock j supplied to the VCO 36 and output from the VCO 36
Is compared with the phase.

The phase comparator 33 generates a pulse having a pulse width from the rising edge of the synchronous clock j to the rising edge of the synchronous clock e, and charges and discharges the charge pump 36 with this pulse, which is unnecessary in the low pass filter (LPF) 37. By removing the high frequency component, a phase difference voltage having a level corresponding to the phase difference between the synchronous clocks j and e is generated and supplied to the differential amplifier 38. Similarly, the phase comparator 34 generates a pulse having a pulse width from the rising edge of the synchronous clock f to the rising edge of the synchronous clock j, charges and discharges the charge pump 39 with this pulse, and removes unnecessary high frequency components by the LPF 40. Thus, a phase difference voltage having a level corresponding to the phase difference between the synchronous clocks f and j is generated and supplied to the differential amplifier 38. The differential amplifier 38 obtains the difference signal of the above two phase difference voltages to obtain the VCO 35.
The VCO 35 oscillates at a frequency according to the level of the difference signal. That is, the VCO 35 generates the synchronous clock j as shown in FIG. 2 (J) which rises at the center position between the rising edge of the synchronous clock f and the rising edge of the synchronous clock e, and the terminal 41
Output from.

This synchronous clock j is supplied to the data discriminating section 18 in FIG. The data discriminating unit 18 synchronizes the composite signal i with the synchronization clock j to obtain the reproduction data shown in FIG. The terminal 20 outputs the synchronous clock j.

Here, the synchronous clock j shown in FIG.
From the rising edge of the synchronous clock j with the period of T as T
The signal g (shown in FIG. 4C) in the range of 4 is phase-shifted to the rising position of the synchronization clock j to obtain the reproduction data shown in FIG. 4D. At the same time, a signal h (shown in FIG. 4B) in the range of ± T / 2 from the rising edge of the synchronization clock j is phase-shifted to the rising edge of the synchronization clock j to be reproduced data. That is, the signal g is allowed from the rising edge of the synchronous clock j to a phase shift of ± T / 2 or less, and in synchronization with this, the signal h is ± T / from the rising edge of the synchronous clock j.
A phase shift of 2 or less is allowed. That is, the phase shift between the signals g and h is allowed up to ± T, and up to twice the phase shift of the conventional one is allowed.

[0024]

As described above, according to the magneto-optical disk reproducing method of the present invention, the allowable range of the phase shift between the rising edge signal and the falling edge signal can be expanded, and the recording mark can be reduced to achieve high density recording. Even if it is performed, highly accurate reproduction becomes possible, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram of the system of the present invention.

FIG. 2 is a signal timing chart of each part of FIG.

FIG. 3 is a block diagram of a clock generation unit.

FIG. 4 is a signal timing chart for explaining the system of the present invention.

FIG. 5 is a diagram for explaining edge recording.

FIG. 6 is a block diagram of a conventional method.

FIG. 7 is a signal timing chart of each part of FIG.

FIG. 8 is a signal timing chart for explaining a conventional method.

[Explanation of symbols]

11 Binarization unit 12 Front and rear edge separation section 13,15 PLL 14,16,18 Data Discrimination Department 17 Synthesis Department 30 clock generator 33,34 Phase comparator 35 VCO 36,39 Charge pump 37,40 low pass filter 38 Differential amplifier

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-230372 (JP, A) JP-A-61-214278 (JP, A) JP-A-5-74057 (JP, A) JP-A-4- 186925 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 20/10 G11B 20/12 G11B 20/14 G11B 20/16 G11B 11/105 H03L 7/00 H04L 7/00

Claims (2)

(57) [Claims] 1. A recording mark is formed on a magneto-optical disk medium having a perpendicular magnetization film by forming a recording mark with an edge position corresponding to the recording data and irradiating the recording mark with a reproducing light spot. Rising edge signals and trailing edge signals indicating the leading edge and the trailing edge, respectively, are detected, and the first and first edges obtained from the rising edge signal and the falling edge signal, respectively.
After the rising edge signal and the falling edge signal are discriminated from each other by using the second synchronous clock, the data discriminating signals of both of them are combined, and the data is discriminated by using the third synchronous clock. And a clock generator (30) for generating a third synchronous clock synchronized with the central position of the phase difference between the first synchronous clock and the second synchronous clock. A magneto-optical disk reproducing method characterized by. 2. The magneto-optical disk reproducing method according to claim 1, wherein the clock generation unit (30) generates a phase difference voltage according to a phase difference between the third synchronization clock and the first synchronization clock. A first phase difference detector (33, 36, 37) and a second phase difference detector (3) that generates a phase difference voltage according to the phase difference between the second synchronous clock and the third synchronous clock.
4, 39, 40), a differential section (38) for obtaining a difference voltage of the phase difference voltages of the first and second phase difference detecting sections, and an oscillation frequency according to the difference voltage obtained by the differential section. A magneto-optical disk reproducing system characterized by comprising an oscillating section (35) for varying the.